Feature Request: Bearer Auth - allow custom error response content type

[max-got]

What is the feature you are proposing?

Problem

Bearer auth error responses can't be sent as anything other than application/json or text/plain. The content type is hardcoded in throwHTTPException...

Request

Since we want to adhere to RFC 9457 problem details (application/problem+json) everywhere, it would be nice if we are able to customize the content type in the response. Since the middleware throws an HTTPException with a pre-built res, an onError handler can't fix the headers afterwards either. See for Reference bearer-auth/index.ts

Idea

Let MessageFunction also return a Response and use it as-is (set WWW-Authenticate if missing). Backwards compatible. Alternatively a contentType option next to message (?)

Current workaround: throw from the message function and rebuild the WWW-Authenticate header manually in the app.

[Jr-14]

Just learnt about RFC 9457 and thought it was pretty cool! I think it'd be really helpful to see first class support for application/problem+json in Hono, especially its strong type inference around request/response types and RPC. I'd definitely use this in our production environments 👍🏼

[Jr-14]

This might be in consideration for this v5 comment #5106 (comment)

[yusukebe]

Hi @max-got

Thank you for the request. I think the middleware should allow users to set error responses flexibly. Letting MessageFunction return Response is one of the solutions, but we have to consider.

If it doesn't introduce a breaking change, we can include it in a minor version update. Don't need to include v5.

[AiAlchemist0]

Opened https://github.com/honojs/hono/pull/ so message can return a Response (RFC 9457) without breaking existing string/object messages.